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rbd: use rwsem to protect header updates 

Updating an image header needs to be protected to ensure it's
done consistently.  However distinct headers can be updated
concurrently without a problem.  Instead of using the global
control lock to serialize headder updates, just rely on the header
semaphore.  (It's already used, this just moves it out to cover
a broader section of the code.)

That leaves the control mutex protecting only the creation of rbd
clients, so rename it.

This resolves:
    http://tracker.ceph.com/issues/5222

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>
This commit is contained in:
Alex Elder 2013-05-31 17:40:45 -05:00 committed by Sage Weil
parent 1ba0f1e797
commit cfbf6377b6
1 changed files with 10 additions and 16 deletions
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26
drivers/block/rbd.c
View File

@ -372,7 +372,7 @@ enum rbd_dev_flags {
RBD_DEV_FLAG_REMOVING, /* this mapping is being removed */
};
static DEFINE_MUTEX(ctl_mutex); /* Serialize open/close/setup/teardown */
static DEFINE_MUTEX(client_mutex); /* Serialize client creation */
static LIST_HEAD(rbd_dev_list); /* devices */
static DEFINE_SPINLOCK(rbd_dev_list_lock);
@ -516,7 +516,7 @@ static const struct block_device_operations rbd_bd_ops = {
/*
* Initialize an rbd client instance. Success or not, this function
* consumes ceph_opts. Caller holds ctl_mutex.
* consumes ceph_opts. Caller holds client_mutex.
*/
static struct rbd_client *rbd_client_create(struct ceph_options *ceph_opts)
{
@ -673,13 +673,13 @@ static struct rbd_client *rbd_get_client(struct ceph_options *ceph_opts)
{
struct rbd_client *rbdc;
mutex_lock_nested(&ctl_mutex, SINGLE_DEPTH_NESTING);
mutex_lock_nested(&client_mutex, SINGLE_DEPTH_NESTING);
rbdc = rbd_client_find(ceph_opts);
if (rbdc) /* using an existing client */
ceph_destroy_options(ceph_opts);
else
rbdc = rbd_client_create(ceph_opts);
mutex_unlock(&ctl_mutex);
mutex_unlock(&client_mutex);
return rbdc;
}
@ -833,7 +833,6 @@ static int rbd_header_from_disk(struct rbd_device *rbd_dev,
/* We won't fail any more, fill in the header */
down_write(&rbd_dev->header_rwsem);
if (first_time) {
header->object_prefix = object_prefix;
header->obj_order = ondisk->options.order;
@ -862,8 +861,6 @@ static int rbd_header_from_disk(struct rbd_device *rbd_dev,
if (rbd_dev->mapping.size != header->image_size)
rbd_dev->mapping.size = header->image_size;
up_write(&rbd_dev->header_rwsem);
return 0;
out_2big:
ret = -EIO;
@ -3333,7 +3330,7 @@ static int rbd_dev_refresh(struct rbd_device *rbd_dev)
int ret;
rbd_assert(rbd_image_format_valid(rbd_dev->image_format));
mutex_lock_nested(&ctl_mutex, SINGLE_DEPTH_NESTING);
down_write(&rbd_dev->header_rwsem);
mapping_size = rbd_dev->mapping.size;
if (rbd_dev->image_format == 1)
ret = rbd_dev_v1_header_info(rbd_dev);
@ -3343,7 +3340,8 @@ static int rbd_dev_refresh(struct rbd_device *rbd_dev)
/* If it's a mapped snapshot, validate its EXISTS flag */
rbd_exists_validate(rbd_dev);
mutex_unlock(&ctl_mutex);
up_write(&rbd_dev->header_rwsem);
if (mapping_size != rbd_dev->mapping.size) {
sector_t size;
@ -4272,16 +4270,14 @@ static int rbd_dev_v2_header_info(struct rbd_device *rbd_dev)
bool first_time = rbd_dev->header.object_prefix == NULL;
int ret;
down_write(&rbd_dev->header_rwsem);
ret = rbd_dev_v2_image_size(rbd_dev);
if (ret)
goto out;
return ret;
if (first_time) {
ret = rbd_dev_v2_header_onetime(rbd_dev);
if (ret)
goto out;
return ret;
}
/*
@ -4296,7 +4292,7 @@ static int rbd_dev_v2_header_info(struct rbd_device *rbd_dev)
ret = rbd_dev_v2_parent_info(rbd_dev);
if (ret)
goto out;
return ret;
/*
* Print a warning if this is the initial probe and
@ -4317,8 +4313,6 @@ static int rbd_dev_v2_header_info(struct rbd_device *rbd_dev)
ret = rbd_dev_v2_snap_context(rbd_dev);
dout("rbd_dev_v2_snap_context returned %d\n", ret);
out:
up_write(&rbd_dev->header_rwsem);
return ret;
}